STUDIES ON DEFINING HETEROTIC GENE POOLS USING MOLECULAR MARKERS IN PEARL MILLET [Pennisetum glaucum (L.)R. Br.]
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Date
2017
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Acharya N.G. Ranga Agricultural University
Abstract
Pearl millet inbred lines comprising of 161 B- and 182 R- lines were
molecularly profiled using 88 polymorphic SSR markers to study genetic diversity
and to define heterotic groups based on genetic distance. Inbred lines were also
evaluated using 12 quantitative characters viz., days to 50 per cent flowering, plant
height, ear length, ear diameter, productive tillers per plant, head yield per plant, grain
yield per plant, panicle harvest index, fresh stover yield per plant, dry matter yield per
plant, 1000 grain weight and grain harvest index to study phenotypic diversity and to
compare genetic and morphological diversity patterns. The selected inbred lines from
heterotic groups were crossed in a line × tester design during Summer, 2015 at
RM01B field, ICRISAT, Patancheru. Evaluation of 122 genotypes (9 lines, 11 testers
and 99 hybrids with three checks viz., HHB 67 Improved, ICMH 356 and HHB 146-
672) was done based on 12 quantitative characters during Kharif, 2015 over two
locations viz., RP 01B field, ICRISAT, Patancheru and Agricultural Research Station,
Vizianagaram and at one location during Rabi, 2015 at Agricultural College Farm,
Naira to study gene action, combining ability, heterosis for yield and its component
traits and to identify the association between genetic distance with F1 mean, heterosis
and specific combining ability for grain yield.
The SSR markers detected a total of 532 alleles with an average of 6.05 alleles
per locus. Of these, 443 and 476 alleles were contributed by B- and R-lines
respectively. Of 532 alleles, 60, 276 and 157 were rare, common and most frequent
alleles respectively. Thirty nine unique alleles which were specific to a particular
accession and useful for germplasm identification were also detected. SSR loci in the
present study identified an average gene diversity of 0.55 and mean PIC of 0.50. Of
88 SSR markers, 5 markers Xipes0203, Xipes0098, Xipes0027, Xipes0233 and
Xpsmp2070 were found to be highly informative with high average number of alleles,
greatest average gene diversity and high average PIC. The unweighted neighborjoining
tree based on simple matching dissimilarity matrix of 347 (one control-Tift
23D2B1P1-P5, repeated 5 times) inbred lines of pearl millet classified into three major
clusters viz., BI, RI, RII and one undetermined cluster which corresponded well with
the pedigree information with minor deviations. The major clusters BI, RI and RII
divided into 10 (1BI, 2BI, 3BI, 4BI, 5BI, 6BI, 8BI, 9BI and 10BI), 9 (2RI, 3RI, 4RI, 5RI,
6RI, 7RI, 8RI and 9RI) and 2 (10RII and 11RII) sub-clusters, respectively. The
representative entries from heterotic groups (10B, 11R-clusters and one undetermined
cluster) defined based on genetic distance were selected for crossing program to
assess the degree of heterosis and hybrid performance for yield in the resulting
crosses. Mantel test showed positive and significant but low correlation between
phenotypic and molecular dissimilarity matrix for both B- and R-lines.
Pooled analysis of variance for combining ability of nine lines selected from
sub-clusters, 1BI (L1), 2BI (L2), 3BI (L3), 4BI (L4), 5BI (L5), 6BI (L6), 8BI (L8), 9BI
(L9) and 10BI (L10), 11 testers selected from sub-clusters, 2RI (T10), 3RI (T11), 4RI
(T12), 5RI(T13), 6RI (T14), 7RI (T15), 8RI (T16), 9RI (T17), 10RII (T18), 11RII (T19)
and undetermined cluster (T20) and 99 F1s with 3 checks, revealed significant
differences among the genotypes for most of the characters studied, indicating a high
degree of variability in the material. Based on pooled mean performance, of 9 crosses
generated from cross between each line with 11 testers, L1T11, L2T12, L3T13,
L4T20, L5T19, L6T11, L7T12, L8T15 and L9T13 had shown higher grain yield per
plant compared to their counterparts.
Based on pooled data, L9 among lines and T11, T12 and T13 among testers
were found as good general combiners for grain yield per plant. Significant positive
specific combining ability (sca) effects were observed among seven hybrids viz.,
L2T12, L3T13, L3T14, L4T20, L5T19, L8T17 and L9T13 for grain yield per plant.
Based on per se performance, high sca effects and standard heterosis in pooled
analysis, two cross combinations viz., L9T13 and L3T13 were found promising over
the best check HHB 146-672 for grain yield per plant.
The correlation between genetic distance and F1 performance, SCA and
heterosis for grain yield per plant was negative and non-significant. Therefore, the
study inferred that genetic distance alone cannot predict heterotic performance of
hybrids. However, utilization of markers specific to yield or QTLs of yield related
traits would be helpful in development of promising hybrids for grain and stover
characters.
The F1s generated from cross between representative entries of cluster 3BI,
10BI with representative entry of cluster 5RI resulted in best heterotic combinations
for grain yield per plant. Moreover, the cross combination resulted from cluster 10BI
and cluster 5RI resulted in best heterotic combinations for most of the characters
under study viz., ear length, productive tillers per plant, head yield per plant, grain
yield per plant, fresh stover yield per plant and dry matter yield per plant.
Description
D5426
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